1. Field of the Invention
The present invention relates to a color selecting method, an image processing method, an image processing apparatus, and a computer-readable recording medium storing a program, for printing a color chart having a plurality of color patches of a reference color and colors close to the reference color with a printing machine, and selecting, from the color chart, one of the color patches which is closest to a designated color.
2. Description of the Related Art
With significant advances in inkjet technology in recent years, it has become possible for inkjet printers to produce large color prints of high quality at high speeds. Inkjet printers are not only popular for private or home use, but nowadays also are widely used in commercial applications. Inkjet printers make it possible to print on POP (point of purchase) posters, wall posters, large-size mediums such as outdoor advertisements and billboards, roll mediums, and thick hard mediums.
There are a wide variety of print mediums (hereinafter also referred to as “mediums”) available for use in prints to meet various commercial demands. For example, such print mediums include paper mediums, such as synthetic paper, thick paper, aluminum-evaporated paper, etc., resin mediums such as those made of vinyl chloride, PET, etc., and tarpaulin paper made of woven fiber cloth with synthetic resin films applied to both surfaces thereof.
Since advertisement prints are expected to be effective to arouse consumers' motivation to buy advertised products through visual sensations of the consumer, the color finish of such prints is of particular importance. Heretofore, there have been disclosed various color matching technologies, such as a method of generating an ICC (International Color Consortium) profile, a method of adjusting a designated color, etc., as a print color managing means. Such color matching technologies are applicable not only to inkjet printers but also to all types of digital printers, including those based on electrophotographic and thermosensitive principles, together with their peripheral devices across the board.
The method of adjusting a designated color referred to above comprises a method of making fine color adjustments of an area of interest in an image in order to bring the color into substantial conformity with a given color (designated color) designated by a color sample of color chips, while maintaining the color balance of the image as a whole. There have been disclosed various methods of adjusting a designated color.
For example, Japanese Laid-Open Patent Publication No. 2000-217007 discloses a method of bringing the impression of a designated color displayed on a display device and the impression of a color printed by a printing machine into conformity with each other. Specifically, Japanese Laid-Open Patent Publication No. 2000-217007 discloses a display window displayed on the display device, in which the displayed color is changeable, and a printed color chart of 27 colors, which are thought to be close to a designated color that is displayed (see FIGS. 4 and 5 of Japanese Laid-Open Patent Publication No. 2000-217007).
The operator sets a designated color that is to be displayed in the display window, presses a print button to print the color chart on the printing machine, selects one of the 27 colors of the color chart, which is closest to the designated color, and enters the number of the closest color into the display device, for thereby strictly approximating the impression of the designated color displayed in the display window by the impression of the color printed on the printing machine.
If the designated color falls within the range of the gamut of the printing machine, then no significant problem arises because at least colors in the neighborhood of the designated color can be reproduced.
On the other hand, if the designated color falls outside the range of the gamut, it is physically impossible to reproduce the designated color. In such a case, the designated color is replaced with a certain color within the gamut, i.e., a color that is closest to the designated color, and a gamut mapping process is carried out taking into account the color balance of the overall image. For determining the certain color, the definition of the “color that is closest to the designated color” is clarified to determine the directionality of an optimum color, and a gamut mapping process (hereinafter also referred to as “mapping process”) is selected.
For example, Japanese Laid-Open Patent Publication No. 2005-084932 discloses a method of and an apparatus for mapping a designated color that falls outside the gamut onto a color within the gamut based on the result of an analysis of the color taste of the operator.
Japanese Laid-Open Patent Publication No. 2002-152535 discloses a method of and an apparatus for changing a mapping process based on an evaluation function depending on the distance up to the gamut if a certain color is judged as a color outside the gamut by a gamut inside/outside determining section.
However, there are instances where even the methods and apparatus disclosed in Japanese Laid-Open Patent Publication No. 2000-217007, Japanese Laid-Open Patent Publication No. 2005-084932, and Japanese Laid-Open Patent Publication No. 2002-152535 fail to select a color that is acceptable by the operator and the client.
According to Japanese Laid-Open Patent Publication No. 2000-217007, when a color chart is to be initially printed, the operator often selects a color (one of 27 colors) corresponding to the designated color by intuition. A color that falls within the gamut but is near its boundary, is highly nonlinear. Reproduction of such a color is difficult to predict, and the color tends to be reproduced with reduced accuracy. If an initial value cannot appropriately be selected, the process of printing and visually checking a color chart has to be repeated many times.
According to Japanese Laid-Open Patent Publication No. 2005-084932 (see FIG. 2 thereof), it is not necessarily clear to the operator how the result of the selection of a color patch is analyzed and reflected. According to Japanese Laid-Open Patent Publication No. 2002-152535, the tendency of a color adjustment based on the evaluation function and the mapping process is not necessarily clear to the operator. Consequently, when the designated color is adjusted, the operator is liable to become more anxious about the possibility not to reach a color that is closest to the designated color as the number of times that a color chart is reprinted increases.